Pure Python CLI that writes Git pack files directly and streams them via Smart HTTP. No git binary, no subprocess. git push recomputes deltas on every push (O(n²)). Streaming pre-built packs lets the server run index-pack (O(n)) instead. REF_DELTA + empty tree SHA-1 = ~80 bytes/commit. ~49,000 commits/sec. 34 min to generate, 3h to push. git fsck --full passes.